It is well-known that it is most efficient for antennas to communicate (i.e., transmit and/or receive) signals from, another antenna when the signal is communicated as a focused beam, rather than as an omni-directional signal. However, when an antenna must simultaneously communicate signals to antennas located in a number of different directions, as with local radio or television stations, it is often advantageous to use less-efficient omni-directional antennas.
One technique that has been employed to communicate signals in multiple directions is to utilize multiple antennas, each of which is configured to communicate signals in one of the multiple directions. It may be appreciated, however, that the employment of multiple antennas is expensive, and often cost-prohibitive.
Commonly, however, antennas that must communicate signals in multiple directions are only required to communicate such signals in one direction at a time. In such cases, alternatives to multiple antennas are available. In one such alternative, a single antenna may be mechanically rotated to direct, or steer, a beam as desired. Mechanically rotated antennas, however, are relatively slow and bulky, and still more expensive than desired.
In another alternative, a phased-array antenna may be used to electronically steer the antenna to transmit or receive a beam in a particular direction, or to find the direction of an incoming beam. A phased-array antenna achieves such functionality by employing a plurality of radiating elements, and a phase shifter configured to alter the input phase at each radiating element, in a manner wellknown in the art. Phase shifters, however, are relatively expensive and, for this reason, phased-array antennas are seldom used, and when they are used, such use is limited to specific applications in which cost is not a significant issue.
Accordingly, a continuing search has been directed to the development of electronically steerable antennas which may be inexpensively fabricated for transmitting and receiving signals in any of a number of different directions, and for direction-finding of an incoming beam.